A relay station (RS) has been proposed to increase the cell coverage and the throughput of a mobile communication system. The RS supports an IEEE 802.16e terminal, has some of the functions of a base station (BS), and performs the functions of an active repeater including mobility, RRM, and security functions and a PMP-based RS network entry function. The RS can remove noise by decoding a signal received from a transmitting end and encoding and transmitting it to a receiving end. The RS also functions as a digital amplifier that can achieve a higher throughput using higher data rate coding. However, the RS has a delay problem that may occur in decoding and encoding processes. The RS also has a problem associated with backward compatibility with PMP mode.
The RS is classified into the following types according to mobility.
1. Fixed RS: This RS is permanently fixed to provide services normally in a shadow area and to increase the cell coverage. This RS can perform simple repeater functions.
2. Nomadic RS: This RS is temporarily installed when the number of users is suddenly increased. This RS can be moved arbitrarily inside a building.
3. Mobile RS: This RS can be installed on mass transportation such as buses or subway trains.
Methods for the RS using frequency bands can be divided into the following three methods.
1. First Method: The RS provides services using a new frequency band different from that used by the BS.
2. Second Method: The RS is assigned the same frequency band as that used by the BS and provides services using the assigned frequency band.
3. Third Method: The RS transfers received control signals or data after simple amplification to the BS using the same frequency band as that used by the BS.
FIG. 1 illustrates a network including an RS. The basic purpose of the RS is to increase the service coverage of the BS or to provide services normally by installing it in a shadow area.
FIG. 2 illustrates an example of a conventional frame structure for the RS.
A downlink (DL) relay zone and an uplink (UL) relay zone for the RS are set in the frame. Data that the BS transmits to the RS is allocated as a burst to a downlink zone of the frame and data that the RS transmits to a mobile terminal or station (MS) is allocated to a downlink zone thereof. When the mobile terminal has data to be transmitted to the BS, the mobile terminal transmits the data using a zone allocated to the terminal in the uplink zone of the RS and the RS include the data into a zone allocated to the RS in the uplink.
FIG. 3 illustrates a conventional OFDMA physical layer frame structure.
A downlink sub-frame starts with a preamble that is used for synchronization and equalization in the physical layer. The preamble is followed by a downlink map (DL-MAP) message and an uplink map (UL-MAP) message which define positions and usages of bursts allocated to the downlink and uplink. The overall structure of the frame is defined by the downlink map (DL-MAP) and uplink map (UL-MAP) messages.
The DL-MAP message defines usages of bursts allocated to a downlink zone in a burst mode physical layer and the UL-MAP message defines usages of bursts allocated to an uplink zone. Information elements (IE), which configure the DL-MAP message, include Downlink Interval Usage Codes (DIUCs), Connection IDs (CIDs), and burst position information (a subchannel offset, a symbol offset, the number of subchannels, and the number of symbols), which allow the user to identify the corresponding downlink traffic intervals. On the other hand, each information element of the UL-MAP message specifies the position of a corresponding interval by a duration defined in the information element and specifies its usage by an Uplink Interval Usage Code (UIUC) for each Connection ID (CID). That is, the usages of the intervals of the UL-MAP message are defined by corresponding UIUCs used in the UL-MAP message. The interval of each UL-MAP information element (IE) starts at a position at a distance, corresponding to a duration defined in a previous UL-MAP IE, from the start of the previous UL-MAP IE.
The following is a more detailed description of the UL-MAP message.
The UL-MAP message is used to assign the grant to use an uplink channel. Consecutive IEs that define usages of the uplink intervals are used to define the usages of uplink bursts and to define the usages of uplink resources assigned to them in units of OFDMA symbols and subchannel blocks.
UL-MAP Information Elements (IEs) will now be described.
The UL-MAP IEs specify information regarding band allocation to the uplink. Each UL-MAP message includes at least one IE in order to indicate the end of the last burst. The order of IEs transmitted through the UL-MAP is determined by a physical layer used. The CID assigns the IE to unicast, multicast, and broadcast addresses. A basic CID of the mobile terminal is used as the CID when a bandwidth grant is explicitly set to be assigned. The UIUC is used to specify a usage of the uplink and its associated uplink burst profile. In the case of each UIUC for use in the UL-MAP message, it is necessary that an Uplink_Burst_Profile be included in an Uplink Channel Descriptor (UCD). All the IEs must be supported by terminals. The BS may use any of these IEs when creating a UL-MAP message.
The following Tables 1 to 3 illustrate examples of the DL-MAP message and the UL-MAP message.
TABLE 1SyntaxSizeNotesDL-MAP_IE( ) {DIUC4bitsif (DIUC == 15) {Extended DIUCvariableSee clauses followingdependent IE8.4.5.3.1} else {if (INC_CID == 1) {The DL-MAP starts withINC_CID = 0. INC_CID istoggled between 0 and 1 bythe CID-SWITCH_IE( )(8.4.5.3.7)N_CID8Number of CIDs assigned forbitsthis IEfor (n=0; n< N_CID;n++) {CID16 bits}}OFDMA Symbol offset8bitsSubchannel offset6bitsBoosting3000: normal (not boosted);bits001:+6 dB; 010: −6 dB; 011: +9 dB;100:+3 dB; 101: −3 dB; 110: −9 dB;111: −12 dB;No. OFDMA Symbols7bitsNo. Subchannels6bitsRepetition Coding20b00 - No repetition codingIndicationbits0b01 - Repetition coding of2 used 0b10 - Repetitioncoding of 4 used 0b11 -Repetition coding of 6 used}}
TABLE 2SyntaxSizeNotesUL-MAP_Message_Format( ) {Management Message Type = 38bitsreserved8Shall be set tobitszero.UCD Count8bitsAllocation Start Time32 bitsBegin PHY Specific Section {See applicable PHYsection.if (WirelessMAN-OFDMA) {No. OFDMA symbols8Number of OFDMAbitssymbols in the ULsubframe}for (i= 1; i <= n; i++) {For each UL-MAPelement 1 to n.UL-MAP_IE( )variableSee correspondingPHY specification.}}if !(byte boundary) {Padding Nibble4Padding to reachbitsbyte boundary.}}
TABLE 3SizeSyntax(bits)NotesUL-MAP_IE( ) {CID16UIUC4if (UIUC == 11) {Extended UIUC 2variableSee subclausedependent IE8.4.5.4.4.2}elseif (UIUC == 12) {OFDMA symbol offset8Subchannel offset7No. OFDMA symbols7No. subchannels7Ranging method20b00 - InitialRanging/Handover Rangingover two symbols0b01 - InitialRanging/Handover Rangingover four symbols0b10 - BWRequest/Periodic Rangingover one symbol0b11 - BWRequest/Periodic Rangingover three symbolsDedicated ranging10: the OFDMA region andindicatorRanging Method definedare used for the purposeof normal ranging1: the OFDMA region andRanging Method definedare used for the purposeof ranging usingdedicated CDMA code andtransmissionopportunities assignedin the MOB_PAG-ADVmessage or in theMOB_SCN-RSP message.} else if (UIUC == 13){PAPR_Reduction_and_Safe-32ty_Zone_Allocation_IE} else if (UIUC == 14){CDMA_Allocation_IE( )32} else if (UIUC == 15){Extended UIUC dependentvariableSee subclauses followingIE8.4.5.4.3} else if (UIUC == 0) {FAST-32FEEDBACK_Allocation_IE()} else {Duration10In OFDMA slots (see8.4.3.1)Repetition coding20b00 - No repetitionindicationcoding0b01 - Repetition codingof 2 used0b10 - Repetition codingof 4 used0b11 - Repetition codingof 6 usedif (AAS or AMC UL Zone)AAS/AMC Allocations{include absolute slotoff-set.Slot offset12Offset from start of theAAS or AMC zone for thisallocation, specified inslots.}}}
The following is a description of how a CQICH channel and a REP-REQ/RSP MAC management message are used in a conventional method for a BS requesting downlink signal quality information of a mobile terminal in a mobile communication system.
(1) CQICH Channel
In one method in which the BS acquires downlink signal quality information of a mobile terminal, respective subchannels to be used for terminals are set after a specific zone in a two-dimensional uplink map is previously assigned as a dedicated channel zone.
As shown in FIG. 3, a slot is set for each mobile terminal (MS) using a CQICH_Alloc_IE or a CQICH_Enhance_Allocation_IE after a CQICH channel zone is previously assigned using a FAST-FEEDBACK channel in a UL-MAP IE in a UL-MAP message. For example, a first MS (MS#1) can set CQICH#1, a second MS (MS#2) can set CQICH#2 and CQICH#3, and a third MS (MS#3) can set CQICH#4.
The CQICH_Alloc_IE is used to dynamically assign a CQICH to the uplink of the terminal or to cancel the assigned zone. Once a CQICH is assigned, the terminal transmits signal quality information through the assigned CQICH zone with a duration set in the CQICH_Alloc_IE. If the terminal cancels the assigned CQICH, i.e., sets the duration in the CQICH_Alloc_IE to zero, the terminal transmits no signal quality information to the BS.
The following table illustrates an example CQICH_Alloc_IE.
TABLE 4SyntaxSizeNotesCQICH_Alloc_IE( ) ( ) {Extended UIUC4CQICH = 0x03bitsLength4Length of the message inbitsbytes (variable).CQICH_IDvariableIndex to uniquelyidentify the CQICHresource assigned to theSS. The size of thisfield is dependent onsystem parameter definedin UCD.Allocation offset6Index to the fastbitsfeedback channel regionmarked by UIUC = 0.Period (p)2A CQI feedback isbitstransmitted on the CQICHevery 2p frames.Frame offset3The SS starts reportingbitsat the frame of which thenumber has the same 3 LSBas the specified frameoffset. If the currentframe is specified, theSS should start reportingin eight framesDuration (d)3A CQI feedback isbitstransmitted on the CQIchannels indexed by theCQICH_ID for 10 ×2 dframes.If d == 0, the CQICH isdeallocated.If d == 0b111, the SSshould report until theBS command for the SS tostop.Report configuration1Update to CINR reportincludedbitsconfiguration isincluded.If (report configurationincluded == 1) {Feedback Type20b00 = physical CINRbitsfeedback0b01 = effective CINRfeedback0b10-0b11 = ReservedReport type10: Report for preamblebit1: Report for specificpermutation zoneIf (Report type == 0) {CINR preamble report1The type of preamble-typebitbased CINR report0 - Frequency reusefactor = 1 configuration.1 - Frequency reusefactor = 3 configuration.}Else {report for permutationzone.Zone permutation3The type of zone forbitswhich to report 0b000 -PUSC with ‘use all SC =0’0b001 - PUSC with ‘useall SC = 1’0b010 - FUSC0b011 - Optional FUSC0b100 - Safety Channelregion 0b101 - AMC zone(only applicable to AASmode) 0b110-111 -ReservedZone type20b00 - non-STC zone 0b01-bitsSTC zone0b10 - AAS zone0b11 - reservedZone PRBS_ID2The PRBS_ID of the zonebitson which to reportIf (Zone type == 0b000or 0b001) {Major group indication1If ‘0’ then the reportbitmay refer to anysubchannel in the PUSCzone.If (Major groupindication == 1) {PUSC Major group bitmap6Reported CINR shall onlybitsapply to the subchannelsof PUSC major groups forwhich the correspondingbit is set.Bit #k refers to majorgroup k.}}CINR zone measurement10: measurement from pilottypebitsubcarriers and, if AASzone, from AAS preamble.1: measurement from datasubcarriers}If (feedback type ==Physical CINR feedback0b00) {Averaging parameter1includedbitIf (Averaging parameterincluded == 1) {Averaging parameter4Averaging parameter usedbitsfor deriving physicalCINR estimates reportedthrough CQICH. This valueis given in multiples of1/16 in the range of[1/16 . . . 16/16] inincreasing order. aavg}}}MIMO_permutation_feedback—20b00 = No MIMO andcyclebitspermutation mode feedback0b01 = The MIMO andpermutation modeindication shall betransmitted on the CQICHindexed by the CQICH_IDevery four allocatedCQICH transmissionopportunity. The firstindication is sent on thefourth allocated CQICHframe transmissionopportunity.0b10 = The MIMO modeand permutation modeindication shall betransmitted on the CQICHindexed by the CQICH_IDevery eight allocatedCQICH transmissionopportunity. The firstindication is sent on theeighth allocated CQICHtrans-missionopportunity.0b11 = The MIMO modeand permutation modeindication shall betransmitted on the CQICHindexed by the CQICH_IDevery 16 allocated CQICHtransmission opportunity.The first indication issent on the 16thallocated CQICHtransmission opportunity.PaddingvariableNumber of bits requiredto align to byte length,shall be set to zero.}
(2) REP-REQ/RSP MAC Message
A. REP-REQ (Channel Measurement Report Request)
This message is used when a BS that operates in a band of 11 GHz or less requests downlink channel measurement results such as RSSI and CINR information of a mobile terminal.
The following table illustrates an example report request (REP-REQ) message format.
TABLE 5ASyntaxSizeNotesReport_Request_Message_Format( ) {Management Message Type =836bitsReport Request TLVsvariable}
The following tables illustrate TLV-encoded parameters of the REP-REQ message.
TABLE 5BNameTypeLengthValueReport request1variableCompound
A signal quality information report response message needs to be used to respond to a list of report request channel measurements received by the mobile terminal.
TABLE 5CNameTypeLengthValueReport type1.11Bit #0 = 1 Include DFS BasicreportBit #1 = 1 Include CINR reportBit #2 = 1 Include RSSI reportBit #3-6 aavg\in multiples of1/32 (range [1/32, 16/32])Bit #7 = 1 Include currenttransmit power reportChannel1.21Physical channel number (seenumber8.5.1) to be reported on.(license-exempt bands only)Channel Type1.310b00 = Normal subchannel,request0b01 = Band AMC Channel,0b10 = Safety Channel,0b11 = SoundingZone-specific1.43Bits #0-2: Type of zone on whichphysical CINRCINR is to be reportedrequest0b000: PUSC zone with ‘use allSC = 0’0b001: PUSC zone with ‘use allSC = 1’/PUSC AAS zone0b010: FUSC zone0b011: Optional FUSC zone0b100: Safety Channel region0b101: AMC zone (only applicableto AAS mode)0b110-0b111: ReservedBit #3: 1 if zone for which CINRshould be estimated is STC zone,0 otherwise.Bit #4: 1 if zone for which CINRshould be estimated is AAS zone,0 otherwise.Bits #5-6: PRBS_ID of the zonefor which CINR should beestimated. Ignored for SafetyChannel.Bit #7: Data/pilot-based CINRmeasurement:0 - Report the CINR estimate frompilot subcarriers,1 - Report the CINR estimate fromdata subcarriersBits #8-13: Reported CINR shallonly be estimated for thesubchannels of PUSC major groupsfor which the corresponding bitis set. Bit # (k + 7) refers tomajor group k. Only applicablefor CINR measurement on a PUSCzoneBits #14-17: aavg in multiples of1/16 (range is [1/16, 16/16])Bit #18: 0 - report only mean ofCINR1 - report both mean and standarddeviation of CINRBits #19-23: Reserved, shall beset to zeroPreamble1.51Bits #0-1: Type of preamblephysical CINRphysical CINR measurementrequest0b00 - Report the estimation ofCINR measured from preamble forfrequency reuse configuration = 10b01 - Report the estimation ofCINR measured from preamble forfrequency reuse configuration = 30b10 - Report the estimation ofCINR measured from preamble forband AMC0b11 - ReservedBits #2-5: in multiples of 1/16(range is [1/16, 16/16]) Bit #6: 0 -report only mean of CINR 1 -report both mean and standarddeviation of CINRBit #7: Reserved, shall be set tozero aavgZone-specific1.62Bits #0-2: Type of zone on whicheffectiveeffective CINR is to be reportedCINR request0b000: PUSC zone with ‘use allSC = 0’0b001: PUSC zone with ‘use allSC = 1’/PUSC AAS zone0b010: FUSC zone0b011: Optional FUSC zone0b100: Reserved0b101: AMC zone (only applicableto AAS mode)0b110 - 0b111: ReservedBit #3: 1 if zone for whicheffective CINR should be reportedis STC zone, 0 otherwise.Bit #4: 1 if zone for whicheffective CINR should beestimated is AAS zone, 0otherwise.Bits #5-6: PRBS_ID of the zonefor which effective CINR shouldbe reported. Ignored for SafetyChannel. Bit #7: Data/pilot-basedeffective CINR measurement: 0 -Report the CINR estimate frompilot subcarriers,1 - Report the CINR estimate fromdata subcarriersBits #8-13: Reported effectiveCINR shall only be estimated forthe subchannels of PUSC majorgroups for which thecorresponding bit is set. Bit# (k + 7) refers to major group k.Only applicable for CINRmeasurement on a PUSC zoneBit #14-15: Reserved, shall be setto zeroPreamble1.71Bits #0-1: Type of preamble-basedeffectiveeffective CINR measurementCINR request0b00 - Report the estimation ofeffective CINR measured frompreamble for frequency reuseconfiguration = 10b01 - Report the estimation ofeffective CINR measured frompreamble for frequency reuseconfiguration = 30b10-11 - ReservedBit #2-7: Reserved, shall be setto zeroChannel1.81Bit #0: 1 - include frequencyselectivityselectivity reportreportBit #1-7: Reserved, shall be setto zero
B. REP-RSP (Channel Measurement Report Response)
The mobile terminal uses this message in order to respond to channel measurements listed in a received report request. The terminal transmits a channel measurement report response message including measurement results of channels listed in a received channel measurement report request. The reported channel quality type is determined according to the type of a channel currently used for communication with the BS. The following Table 6A illustrates a channel measurement report response message format.
TABLE 6ASyntaxSizeNotesReport_Response_Message_Format{Management Message Type =837bitsReport Response TLVsvariable}NameTypeLengthValueReport1variableCompoundChannel Type2variableCompoundReport inWirelessMANOFDMA PHYCurrent1471See 8.3.7.4 andtransmitted11.1.1power
A report of channel types and information reported through the channel measurement report response message include parameters as shown in the following Table 6B.
TABLE 6BNameTypeLengthValueREP-REQReport typebit #0 = 1Channel1.11Physical channel number (seenumber8.5.1) to be reported onbit #0 = 1Start1.2216 LSBs of Frame number inframewhich measurement for thischannel startedbit #0 = 1Duration1.33Cumulative measurementduration on the channel inmultiples of Ts. For anyvalue exceeding 0xFFFFFF,report 0xFFFFFFbit #0 = 1Basic1.41Bit #0: WirelessHUMANreportdetected on the channelBit #1: Unknown transmissionsdetected on the channelBit #2: Specific SpectrumUser detected on the channelBit #3: Unmeasured. Channelnot measuredbit #1 = 1CINR1.521 byte: mean (see also 8.2.2,report8.3.9, 8.4.11) for details) 1byte: standard deviationbit #2- 1RSSI1.621 byte: mean (see also 8.2.2,report8.3.9, 8.4.11) for details) 1byte: standard deviationREP-REQChannel Typerequest (binary)01Band2.25First 12 bits for theAMCband indicating bitmapReportand next 20 bits for(CQICINR measurement (5value)bits per each band)11Sounding2.51Average SINR. 8 bits in the sameReportformat used in 8.4.11.3
The RS described above in the conventional technologies can be fixedly installed between a base station (BS) and a terminal. The conventional RS also can be installed on a moving vehicle to increase the service coverage of the BS or to reduce shadow areas.
However, there is no conventional technology which suggests a method for deciding when to perform direct communication between the BS and the terminal and when to perform relay communication through the RS.
The conventional communication system provides a method in which the BS receives, directly from a mobile terminal, signal quality information of downlink/uplink channels between the BS and the mobile terminal. According to this signal quality information of downlink/uplink channels, MS performs handover.
However, no conventional communication technologies provide a method for the communication system including the RS in which the terminal, the RS, and the BS can communicate with each other according to changes of status of radio channel.